Display apparatus



Aug, 23, 1960 C. S. REIS DISPLAY APPARATUS Filed July 20, 1956 3 Sheets-Sheet 1 :I: IE a I: 25

:EIl'fl 2! 61 mm ES 5. 169/5 INVENTOR.

Aug. 23, 1960 c. s. REIS 2,950,418

DISPLAY APPARATUS Filed July 20, 1956 3Sheets-$het 2 Chan 5 5. 14 5/5 IN V EN TOR.

Aug, 23, 1960 c. s. REIS DISPLAY APPARATUS 3 Sheets-Sheet 5 Filed July 20, 1956 BINARY 4 BINAIQYZ BINARY 3 BINARY 4 OUTPUT V3A a a :EIE IEI ii? f if a/af x/a V V V V V3A 28 44 24 4A IIE EI CHARLES 5. Pas

INVENTOR.

nIsrLAY APPARATUS Charles S. Reis, Mountain View, (Ialih, assignor to Hewlett-Packard Company, Palo Alto, Calif., a corporation of California Filed July 20, 1956, Set. N0. 599,115

2 Claims. (Cl. 315-169) This invention relates generally to numerical display apparatus and method and more particularly to a numerical display apparatus and method of the type adapted to give an in-line read-out.

It is an object of the present invention to provide a numerical display apparatus and method which includes a photo-conductive switching matrix.

lt is another object of the present invention to provide a numerical display apparatus and method which employs a plurality of electroluminescent elements disposed whereby any number may be synthesized by exciting the appropriate one of the elements.

it is a further object of the present invention to provide a numerical display apparatus and method which includes a photoconductive switching matrix which is adapted to excite appropriate ones of a plurality of electroluminescent segments used to synthesize a predetermined number.

it is a further object of the present invention to provide a numerical display apparatus and method which employs photoconductive and electroluminescent material to form light amplifying means.

it is further object of the present invention to provide a numerical display apparatus and method in which a photoconductive matrix is illuminated by the display lights of a decade counter, the matrix serving to control the energization of electroluminescent segments which are adapted to synthesize the number representing the count.

It is a further object of the present invention to provide a numerical display apparatus and method which is suit able to give an in-line read-out of information stored in electronic counters and the like.

It is still further object of the present invention to provide a numerical display apparatus which is easily and inexpensively manufactured and which is reliable in operation.

These and other objects of the invention will be understood more clearly and fully from the following detailed description with reference to the accompanying drawings.

Referring to the drawings:

Figure l is a perspective view of a numerical display unit constructed according to my invention;

Figure 2 is a front elevational view of the printed circuit board of Figure 1 showing the elongated conductive segments;

Figure 3 is a back elevational view of the printed cir cuit board showing the inter-digital conductors;

Figure 4 shows a suitable matrix mask which in conjunction with the inter-digital conductors forms the switching photoconductive matrix for controlling the numerical display;

Figure 5 is a schematic circuit diagram showing the connection of the photoconductors, electroluminescent cells and the alternating current source;

Figure 6 is' a sectional view of another embodiment of my invention;

Figure 7 is a back elevational view of the printed circuit board employed in the apparatus of Figure 6;

tates Patent 0 2,950,418 Patented Aug. 23, 1960 Figure 8 is a block diagram of a decade counter; and

Figure 9 is a schematic circuit diagram of the number read-out system for the decade counter of Figure 8.

Referring to Figure 1, a numerical display unit is shown. The unit comprises a glass plate 11, one surface of which has been treated to form a transparent conductive coating 12. For example, the transparent conductive coating may be formed on the surface of the glass by subjecting the same to an atmosphere of stannous chloride in the presence of heat. The transparent coating may also be formed by well known metal evaportion techniques.

An insulating board 13 which preferably is a printed circuit board, as will be presently described, has conductive segments or areas formed on one face. The configuration of the conductive segments or areas will be presently described in detail. The segments are employed in conjunction with electroluminscent material to synthesize a predetermined number. Conductive elements are also formed on the other face. These are employed in conjunction with photoconductive material to form a switching matrix.

The conductive segments or areas are coated with a layer of suitable electroluminescent phosphor 14. As is well known, electroluminescent phosphors serve to generate light when a suitable field is applied thereto. Generally, the field applied is an A.-C. field. The electroluminescent phosphor is applied as a relatively thin coating. -lowever, the thickness should be large in comparison to the particle size of the phosphor employed whereby the cell is uniformly illuminated when the phosphor is energized by the electric field. Generally, coatings having thicknesses varying between .001 to .007 inch are suitable. Voltages of volts or more create a suitable field for this order of thickness. It is, however, to be understood that the thicknesses and voltages given are merely illustrative and that the invention is not to be limited in this respect.

The electroluminescent phosphor is preferably mixed into an air drying binder solution which is applied to the surface. For example, the mixture may be sprayed onto the surface. The conductive surface of the glass plate is then placed in intimate contact with the opposite surface of the electroluminescent layer whereby the layer is sandwiched between the conductive segments or areas formed on the insulating board and the conductive coatmg.

On the opposite side of the insulating board are formed interdigital conductive elements, to be presently described in detail. Alternate ones of the interdigital elements are interconnected through the insulating board to the appropriate one of the numerical segments or elements.

A photoconductive layer 16 is applied over the interdigital conducting elements. The layer may be formed by evaporation, by dusting finely divided crystalline photoconductive particles over a tacky binder coating, or by settling the particles from an appropriate solution. However, I prefer to mix the particles in an air drying binder solution which is then sprayed onto the interdigital elements. A suitable thickness of photoconductive material is formed in this manner. For example, a thickness of .002 inch is satisfactory in most applications.

A matrix mask 17, to be presently described in detail, is applied over the photoconductive material and serves to provide means whereby predetermined areas of the photoconductive layer may be illuminated. When these areas or regions are illuminated, the conductivity of the photoconductive layer increases, as is well known, to thereby interconnect the associated interdigital elements.

A plurality of compartments are provided behind the mask and serve to accommodate a suitable light source. A compartment is included for each numeral to be displayed.

, thesize, the corresponding number.

1 pre vio sly' described, the number is synthesized by illuminating a plurality of segments or areas of the electroluminescent layer disposed between -the conductive layer and the conductive areas or segments .in contact therewith. A suitable configuration of c onduc'tiv'e segments a. through g is shown in Figure 2.

.The'cdnfigurationillustrated is such that by applying an :A.-C-lfield betweenpredetermined ones of the segments 1 fdflthrough. g and theiconductive'layer, any one'of the humanist-9 .may be synthesized. ,I Preferably, the con- :ductiv'e configuration is formedon a printed circuit board byw'e'll known printed circuit techniques. An electric field is applied between the conductive segments or. areas and the conductive'layer to synthesize a predetermined number. Thefield is applied between the :segments and the co-nductiv e layer as follows to synthesize ,the numerals -9: the number 0 by applying a field between the;segments a, b, c, f, gand the conductive layer; the numberl by applying afield between the segments .1; land; or c and e'and the conductive layer; the'number lby'lapplyirig an A.-C. field between the segments b, c, dgg e and the conductive layer; the number 3 by applying a suitable field between the segments b, c, d, e, f and the conductive layer; the number4 by applying a suitable -field between the segments a e, d, e andthe conductive :layer; the number 5 by applying a suitable;A.-C. field between the segments b, c, d, e, f and the conductive layer; the number 6 by applying a field between the segments a, b, d,e, 7, g and the conductive layer; the num- -ber 7 byapplying a field between the segments b, c, e -jand the conductive layer; the number 8 by applying a field between all ofthe segments and the conductive layer; and the number 9 by applying a field between the elements a, b, c, d, e, f and the conductive layer.

. Thefield applied between the segments and the trans- 5 parentcoating may be controlled by a suitable relay -matrix. j The matrix serves to apply a field between the appropriate segments and thetransparent coating to syn- However,.I prefer to employ a photoconductive switching matrix, to be 7 "presently described, which simplifies the constructionand which is simply and inexpensively manufactured.

.. .Referring now to Figure .3, the interdigital conducting elements 23 and 24 formed on the opposite side of the 'insulating. board 13 are illustrated. The elements 23 are connected .with associated ones of the conductive seg- 1-ments.;or regions ag formed on the other side of the insulating board. (schematically illustrated by connecting linesin Figure 3). The conductive elements 23 are dis- ;posed between adjacent ones of the interconnected elements24.l. .As previously described, the interdigital conducting elements may be formed on a printed circuit board 'by well known printed circuit techniques.

The interdigital conductive elements are coated with a'layer'. of photoeon'du ctivematerial, as previously'de- F scribed, whereby when selected regions of the material are illuminated, the region becomes conductive and interconnects the associated ones of the elements 23 with the elements 24 to' thereby form a closed circuit between the elements 24 andthe respective ones of the segments orregions a-.g. a

.In effect, the spaces'between the elements 23 and 2 4 form "a plurality of long photoconductive cells.'- By.

, ewhereb y appropriate ones of the segments a g are connected to the one terminal of a voltage supply connected 'to elements 24. 1 The'oth'er terminal of the voltage supply is suitably connected to the conductive layer 12.

to be displayed 7 4 Thus, as various ones of the elements 23 and 24 are interconnected, a field is applied to the electroluminescent material disposed between the conductive segments ag and the conductive layer whereby appropriate areas 5 of the electroluminescent material are energized and emit light. a

Referring particularly to Figure 4, a suitable matrix mask isrshownwThe mask is formed with. a plurality of openings 26 which are'disposed in rows corresponding to ag and in columns corresponding to '0-9." The columns are located at-the ends of 'the respective light receiving chambers ,27 shown in Figure 1, having lights 28 disposed therein. Each columnis therefore adapted to be illuminated by" one of the lights 28. V 15 The mask may be formed from a sheet of suitable insulating material which is appropriately cut out to form the openings 26. However, I prefer to form the mask by covering the appropriate ones of the regions between the conductors and thenspraying a suitable opaque coatingover the complete layer. Subsequentto the application of the opaque coating, the masking elements are removed'to leave the openings which serve to illuminate the appropriate regions between the elements 23 and 24. Referring particularly to column 1, if the light 28 associated therewith'is energized, the region between the elements 23 associated with the segments c and e and the elements 24 will become conductive thereby interconnecting the one terminal of the power supply to the segments whereby a field is applied across the electroluminescent material to form the numeral 1. Operation of the remaining columns to connect the appropriate segments to the one terminal of the power supply to synthesize a predetermined number is apparent.

It is, of course, to be understood that the disposition of the various openings 26 and the interconnection of the lines 23 may be varied in any desired manner.

Referring to Figure 5, a circuit diagram is shown. The plurality of segments a through g are shown schematically connected in series with the elongated photoconductive cells 29. Each of the photoconductivecells 29 corresponds to rows a through g of Figures 3 and 4. The electroluminescent cells formed by the plurality of segments and the photoconductive layer are numbered athroughg.- r

A suitable A.-C. voltage supply 31 is connected betweenthe interconnected elements 24 and the conduc- -tive layer 12. When the appropriate one of, the photoconductive cells 29'is illuminated, the resistance of the cell is considerably reduced and the voltage is applied -to--the corresponding conductive segments. A field is then imposed" upon the electroluminescent material disposed between", the associated segments a -g and the conductive layer whereby the electroluminescent material =is energized and serves'to' emit light.

In effect a light amplifier'is associated with each of .the' segments whereby the illumination of the bulbs 28 is intensified by the combination of the photoconductive and electroluminescent cells. I It is apparent that 'aplurality of these display units v may be located adjacent one another to form an in-line read-out associated with an electronic counter or the like. Referring to Figure 6, another numerical display unit is illustrated. The unitcomprises a glass plate 41. which has a suitableconductive layer. 42 formed thereon. An 6 insulating board 43.has segments of the type shown in 'Figure' 2 formed on the face 44 thereofi An electroluminescent layer 46 'is formed'on the face 43 and in conductive contact with the conductive segments. 'The f other surface of the layer 46 is' in electrical contact with the conductive layer 42 formed on the glass plate 41. Y The side 47 of the insulating board has conductive ele- :inents of the type shown in Figure 7 formed thereon.

. g A photoconductive layer 48 is applied aspreviously described, and jsfin'electricalcQntaet theconductive lines. A matrix mask 49 of the type previously described and shown in dotted outline with its openings 51 overlying the conductive elements (Figure 7) is applied over the other surface of the photoconductive layer. A second glass plate 52 having a suitable conductive layer 53 is applied over the mask 49 and is in electrical contact with the exposed portions of the photoconductive layer.

The columns of openings are illuminated, as previously described. However, in the unit illustrated in Figures 6 and 7 the photoconductive material between the conductive coating 53 of the glass plate 52 and the associated conductive elements becomes conductive and forms a closed circuit, thus connecting the conductive layer 53 and the associated conductive segment formed on the face 44 of the insulating board 43.

Operation is as previously described for the other embodiment illustrated. Thus, by forming a conductive connection between the layer 53 and the appropriate one of the conducting elements formed on the face 47 of the insulating board 43, the layer is conductively connected to the appropriate one of the segments formed on the race 44. By connecting an appropriate voltage supply,

between the conductive layers 42 and 53, a suitable electric field is applied between predetermined ones of conductive segments and the layer 42 whereby the electroluminescent material -lying adjacent thereto is energized and serves to emit light. Thus, the numeral is synthesized.

The numerical display unit is adapted to be used in conjunction with electronic counters to give an in-line read-out. One unit is associated with each of the decade counters. Generally, electronic counters comprising a plurality of decade counters connected in series and disposed side by side so that the first counter provides the units digit, the second counter provides the tens digit, etc. The final answer is then read directly as a number across a row of counters. The numbers associated with each of the counters are disposed in a column which has the numerals 0-9 formed thereon. Lights are associated with each of the numbers whereby appropriate ones of the numbers are lit corresponding to the count. It is apparent that only for certain numbers will the count be in-line. For other numbers, the eye must be scanned up and down as well as across to obtain a reading.

A typical decade counter is illustrated in block diagram in Figure 8. The four binaries are bi-stable multivibrators having two stable states, (1) with A side conducting, (2) with B side conducting. The four binaries are connected in cascade so that the output from the first is fed to the input of the second, etc. Each binary is designed to respond to negative-going input pulses. Each binary produces alternately positive and negative output pulses for a series of negative input pulses. Since the next binary senses only negative pulses, the eitect is to divide by two.

With four such binaries, sixteen input pulses are required to obtain one negative output pulse. However, by the use of two feedback loops 61 and 62, six extra counts are added within the unit so that only ten input pulses are required to obtain one negative output pulse to make a total division of ten. The feedback circuits used w th the counters are not to be confused with the feedback circuits used in amplifier design. Counter feedback circuits are used only to apply a pulse from one of the binary in a pair to another in the same binary. If the feedback pulse is of the corresponding polarity, it will trigger the binaries, producing the same result as an additional pulse to the input.

As the binaries sense the input pulses, certain combinations of voltages are set up between the halves of the binaries which light the appropriate neon lamp for each pulse. Referring to Figure 9, a suitable network is shown which serves to light the appropriate one of the numerals. The state of the first binary 63 determines whether an odd or even numbered lamp will be lighted by applying one necessary voltage to the even lamps, or to the odd lamps. The other voltage is obtained as the difierence voltage existing across two specific halves of two different binaries. As subsequent input pulses are received, the difference voltage lighting the lamps proceeds from one pair of binaries to the next, lighting subsequent lamps.

The binary 63 has one half connected to all of the even numbered lamps and the other half connected to one side of all of the odd numbered lamps. As the binary switches back and forth, it alternately supplies one needed voltage to light the odd, and then the even numbered lamps. The difierence voltage which determines which odd or even lamp is lighted is obtained from a combination of the various halves of the remaining three binaries and consists of a resultant voltage. When two different binary halves are combined, three resultant voltages are possible; when both halves are conducting, when both halves are not conducting, and when one is conducting and when one is not. Only when both halves are con ducting and the voltage is at its lowest is the voltage difference between the combinations and that established by the input binary sulficient to light a neon. This voltage gradually moves down the bank of neons as shown in the diagram as succeeding input pulses switch the binaries and the odd-even lamps are alternately given the necessary voltage.

When using the numerical display unit with decade counters of the type described, the neon lamps are disposed in the chambers 27 and serve to illuminate the openings 26 of the matrix mask whereby the appropriate segments ag are connected to the terminal of the voltage supply. The resultant field applied between the segments and the conductive surface serves to energize the electroluminescent material and to synthesize the appropriate number.

A display unit was constructed as shown in Figure 1. The transparent conductive coating was formed on a glass plate by subjecting the glass to a stannous chloride atmosphere in an oven which was operated at a temperature of 1150 F. The conductive segments and interdigital elements were formed by printed circuit techniques. The conductive segments were of the form shown in Figure 2 with horizontal segments having a length of inch and a width of A inch, and the vertical segments having a length of /2 inch and a width of inch. The electroluminescent material consisted of zinc sulfidezcopper activated and was dispersed in an epoxy resin and applied to a thickness of .003 inch.

The interdigital elements 24 were 4 inches long and inch Wide and were interconnected as shown. The interdigital elements 23 were 4 inches long and & inch wide. The elements 23 were connected through the in sulating board to the associated segment formed on the other side of the board. The photoconductive coating applied over the interdigital lines was .002 inch in thickness and consisted of cadmium sulfide:copper activated. The matrix mask had openings as shown in Figure 4, which openings were inch long and 4 inch Wide. A voltage of 600 volts having a frequency of 400 c.p.s. was applied between the conductive coating 12 and the interdigital elements 24.

The neon lamps were lamps associated with a decade counter known by manufacturers specification as Decade Counter AC-4A, sold by Hewlett-Packard Company, Palo Alto, California.

The apparatus constructed in accordance with the above was operated and the numerical display was appropriately synthesized.

Thus it is seen that a novel numerical display unit has been described. The unit serves to provide means whereby an in-line read-out is easily obtained. The unit is simply and inexpensively manufactured and is reliable in operation.

1 7 I.;I"claim: m J T. T j' ".1: 1. A display apparatus comprising an insulating board; 'a plurality of conductive segments disposed in a predeterminedmanner on one surface of said board, a layer of electroluminescent material disposed over said one surface. of said board and said' segments,ia transparent conductive la'yerin electrical contact with the exformed on the other surface of the insulating board and connected to said conductive segments, a photoconductiveflayer disposed over said conductive lines, a matrix mask having openings disposed in a predetermined manner placed ;over;the1other surface of said photoconduclive glayer an'd a jtransparent;condu ctive layer making electrical contact with the photoconductive materialplying opposite saidopenings. 1 1 w V j References Cited in the fileof this patent UNITEDVSTATES PATENTS 1,779,748 I Nicols'on Oct. 28; 1930 2 ,471,253 Toulon May 24,1949 2,500,929 Chilowsky Mar. 21, 1950 2,558,019 Toulon June 26, 195 1 2,698,915 Piper Ian. 4, 1955 2,768,310 7 Kazan Oct. 23, 1956 m a. a.) 

